Plasma mediated ashing processes that include formation of a protective layer before and/or during the plasma mediated ashing process

ABSTRACT

Processes for stripping high dose ion implanted photoresist while minimizing substrate loss. The processes generally include passivation of the substrate surface before and/or during a plasma mediated stripping process. By passivating the substrate surface before and/or during the plasma mediated stripping process, oxidation is substantially reduced during plasma stripping thereby leading to reduced substrate loss.

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims the benefit of the legallyrelated U.S. Provisional Patent Application Ser. No. 61/033,969 filedMar. 5, 2008, and U.S. Provisional Patent Application Ser. No.61/037,589; filed Mar. 18, 2008; both provisional applications are fullyincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present disclosure generally relates to plasma mediated ashingprocesses that include formation of a protective layer before and/orduring a plasma mediated ashing process.

Plasma mediated ashing, also referred to as stripping, generally refersto an integrated circuit manufacturing process by which residual organicmaterial such as photoresist and post etch residues are stripped orremoved from a substrate upon exposure to the plasma. The ashing processgenerally occurs after an etching or implant process has been performedin which a photoresist material is used as a mask for etching a patterninto the underlying substrate or for selectively implanting ions intothe exposed areas of the substrate. The remaining photoresist and anypost etch or post implant residues on the wafer after the etch processor implant process is complete must be removed prior to furtherprocessing for numerous reasons generally known to those skilled in theart. The ashing step can be followed by a wet chemical treatment toremove traces of the residue.

It is important to note that ashing processes significantly differ frometching processes. Although both processes may be plasma mediated, anetching process is markedly different in that the plasma chemistry ischosen to permanently transfer an image into the substrate by removingportions of the substrate surface through openings in a photoresistmask. The etching plasma generally includes high-energy ion bombardmentat low temperatures and low pressures (of the order of millitorr) toremove portions of the substrate. Moreover, the portions of thesubstrate exposed to the ions are generally removed at a rate equal toor greater than the removal rate of the photoresist mask. In contrast,ashing processes generally refer to selectively removing the photoresistmask and any polymers or residues formed during etching. The ashingplasma chemistry is much less aggressive than etching chemistries and isgenerally chosen to remove the photoresist mask layer at a rate muchgreater than the removal rate of the underlying substrate. Moreover,most ashing processes heat the substrate to temperatures greater than80° C. to increase the plasma reactivity, and are performed atrelatively higher pressures (on the order of a torr). Thus, etching andashing processes are directed to removal of significantly differentmaterials and as such, require completely different plasma chemistriesand processes. Successful ashing processes are not used to permanentlytransfer an image into the substrate. Rather, successful ashingprocesses are defined by the photoresist, polymer and residue removalrates without affecting or removing underlying layers, e.g., thesubstrate, low k dielectric materials, and the like.

As devices transition into the 32 nanometer (nm) regimes and beyond,there is growing concern with plasma mediated damage caused by plasmamediated stripping processes. One such area of concern is with theremoval of photoresist exposed to high doses during ion implantation inthe transistor formation. Typically, sensitive substrate materials suchas silicon (implanted, often with very shallow dopants), SiGe, high-kdielectrics, metal gates, etc. are exposed during the photoresistremovable process and substrate damage can occur. The substrate damagemay be in the form of substrate erosion (e.g., etching, sputtering,physical removal of a portion of the substrate) or by substrateoxidation. The substrate oxidation is undesirable as it will change theelectrical, chemical, and physical properties of the substrate layer.For example, in a source and drain implant application, a patternedphotoresist layer is formed over the silicon substrate at the source anddrain regions prior to carrying out a high dose implant. During the highdose implant, the photoresist is subjected to high energy ions thatinduce cross-linking reactions to harden an upper shell of thephotoresist, commonly referred to as the crust. The physical andchemical properties of the crust vary depending on the implantconditions. Because of this, more aggressive chemistries are needed toremove the resist. At the same time, however, extremely shallow junctiondepths are calling for very high selectivity. Silicon loss or siliconoxidation from the source/drain regions must be avoided during thehigh-dose ion implantation strip. For example excessive silicon loss candeleteriously alter the current saturation at a given applied voltage aswell as result in parasitic leakage due to decreased junction depthdetrimentally altering electrical functioning of the device. TheInternational Technology Roadmap for Semiconductors (ITRS) projectstarget silicon loss for the 45 nm generation to be 0.4 angstroms percleaning step and 0.3 angstroms for the 32 nm generation.

Current plasma mediated stripping processes are typically oxygen basedfollowed by a wet clean step. However, oxygen based plasma processes canresult in significant amounts of substrate surface oxidation, typicallyon the order of about 10 angstroms or more. Because silicon loss isgenerally known to be governed by silicon surface oxidation for plasmaresist stripping processes, the use of these oxygen based plasma stripprocesses by themselves is considered by many to be unacceptable for 45and 32 nm technology node where almost “zero” substrate loss is requiredand new materials are introduced such as embedded SiGe source/drain,high-k gate dielectrics, metal gates and NiSi contact which areextremely sensitive to surface oxidation.

Accordingly, there remains a need for improved photoresist resiststripping processes, especially as it relates to the removal ofphotoresist exposed to high dose implantation.

BRIEF SUMMARY OF THE INVENTION

Disclosed herein are processes and systems for reducing the loss ofsubstrate material in a plasma mediated photoresist stripping process.In one embodiment, a process for reducing the loss of substrate materialin a plasma mediated photoresist stripping process comprises providing asubstrate having at least a portion of a surface covered with amaterial; forming a protective layer on the surfaces free of thematerial before and/or during the photoresist stripping process, whereinforming the protective layer comprises exposing the substrate to plasmaformed from a nitrogen containing gas and/or a carbon containing gas orexposing the substrate to ultraviolet radiation in the presence of thenitrogen containing gas and/or the carbon containing gas; simultaneouslyremoving at least a portion of the material with the plasma mediatedstripping process and the protective layer; and repeating the steps offorming the protective layer and removing the at least portion of thematerial disposed thereon until a desired thickness of the material isremoved.

In another embodiment, a process for reducing the loss of substratematerial in a plasma mediated photoresist stripping process, the processcomprises providing a substrate including a mask of an organic materialdisposed thereon; forming a protective layer on an exposed surface ofthe substrate without the mask before and/or during the photoresiststripping process, wherein forming the protective layer comprisesexposing the surface to ultraviolet radiation in the presence of aninert gas or a nitrogen containing gas or a carbon containing gas ormixtures thereof, removing at least a portion of the mask and theprotective layer with the plasma mediated stripping process; andrepeating the steps of forming the protective layer and removing the atleast portion of the mask until a desired thickness of the mask isremoved.

A plasma processing system for processing an inorganic workpiecesubstrate having organic material residing thereon by removing theorganic material while leaving the inorganic substrate substantiallyunaltered, comprises a process chamber for processing the workpieceplaced therein; a plasma source for delivering excited state gas intosaid process chamber to produce a reactive environment therein; a gasdelivery system, including a plurality of gas valves, for selectivelydelivering at least one gas from a gas supply to said plasma source; apower generator assembly for powering the plasma source to excite thegas delivered by said gas delivery system; and a control system forselectively activating said gas valves of said gas delivery system so asto provide at least a first selected gas for at least a first selectedtime interval for forming a protective layer on the substrate, and atleast a second selected gas for at least a second selected time intervalfor removing the organic material residing on the workpiece substrate.

These and other features and advantages of the embodiments of theinvention will be more fully understood from the following detaileddescription of the invention taken together with the accompanyingdrawings. It is noted that the scope of the claims is defined by therecitations therein and not by the specific discussion of features andadvantages set forth in the present description.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of the embodiments of the inventioncan be best understood when read in conjunction with the followingfigures, which are exemplary embodiments, in which:

FIG. 2 schematically illustrates a process that includes plasma mediatedformation of a silicon oxy-nitride (SiO_(x)N_(y)) passivation layerbefore or during the plasma strip process;

FIG. 3 schematically illustrates a process that includes UV formation ofa passivation layer before or during the plasma strip process;

FIG. 4 is a bar chart illustrating atomic nitrogen concentrationdetected by X-ray Photoelectron Spectroscopy (XPS) analysis for asilicon substrate exposed to a nitrogen passivation plasma, a standardoxygen based plasma recipe, and a no ash control sample;

FIG. 5 graphically illustrates high resolution XPS spectra of the Si(2p) signal for a silicon substrate exposed to a nitrogen passivationplasma, a standard oxygen based plasma recipe, and a no ash controlsample;

FIG. 6 graphically illustrates Secondary Ion Mass Spectroscopy (SIMS)depth profile of nitrogen and oxygen for a silicon substrate exposed tonitrogen-containing plasma;

FIG. 7 graphically illustrates oxide thickness as a function ofpassivation and ashing cycle time for a silicon substrate for both preash and post ash conditions, wherein the total passivation time for eachsubstrate was 60 seconds and the total standard oxygen based plasmaashing exposure time was 60 seconds;

FIG. 8 is a bar chart illustrating oxide growth as a function ofexposure to different oxidizing and reducing plasma chemistries with andwithout a UV pretreatment. The UV passivation exposure time was 5minutes and the plasma strip exposure time was 30 seconds;

FIG. 9 is a bar chart illustrating atomic surface concentration detectedby XPS as a function of UV exposure and no UV exposure for carbon,nitrogen, oxygen and silicon species; and

FIG. 10 graphically illustrates high resolution XPS spectra of nitrogen,N (is), for silicon substrates processed with and without exposure toUV-NH₃.

Skilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale.

DETAILED DESCRIPTION OF THE INVENTION

Disclosed herein are processes and systems for reducing the loss ofsubstrate material in a plasma mediated photoresist stripping process.The processes and systems are generally configured to cycle betweenformation of a protective layer on and/or in an exposed substratesurface and ashing of organic material (e.g., a photoresist mask,anti-reflection coating, and the like) from the substrate surface. Asnoted above, the protective layer can be applied onto the surface (e.g.,via deposition) and/or may be formed in the surface (e.g., viapassivation) before and/or during the plasma mediated stripping process.The protective layer serves to protect the exposed surfaces of thesubstrate from any plasma mediated damage that may occur during theplasma mediated stripping process for removing organic material. Theprotective layer can be formed via plasma treatment or by ultravioletradiation (UV) treatment.

Turning now the embodiment shown in FIG. 1, the system 10 for reducingthe loss of substrate material in a plasma mediated photoresiststripping process generally includes a process chamber 12 for processingthe workpiece 14 placed therein; a plasma source 16 for deliveringexcited state gas into said process chamber 12 to produce a reactiveenvironment therein; a gas delivery system 18, including a plurality ofgas valves 20, for selectively delivering at least one gas from a gassupply 22 to said plasma source 16; a power generator assembly 24 forpowering the plasma source to excite the gas delivered by the gasdelivery system 18; and a control system 26 for selectively activatingsaid gas valves 20 of said gas delivery system 18 so as to provide atleast a first selected gas for at least a first selected time intervalfor forming a protective layer on the substrate, and at least a secondselected gas for at least a second selected time interval for removingthe organic material residing on the workpiece substrate.

The processes can be practiced in conventional plasma ashers and are notintended to be limited to any particular plasma asher. For example, aplasma asher employing an inductively coupled plasma reactor could beused or a downstream plasma asher could be used. Other suitable plasmaashers include, but are not limited to, electron cyclotron residence(ECR) systems, radio frequency (RF) systems, hybrid systems, and thelike. In one embodiment, the plasma asher is a downstream plasma asher,such as for example, microwave plasma ashers commercially availableunder the trade name RadiantStrip ES31lk® from Axcelis Technologies,Inc. in Beverly, Mass. Preferably, the plasma asher provides a stableplasma that can tolerate the variations in gases provided by the cyclingbetween formation of a protective layer on and/or in an exposedsubstrate surface and ashing of organic material from the substratesurface.

The gas supply includes a plurality of gases, which may include reactivegases and/or inert gases. As used herein the term “reactive gas”generally refers to gases that provide plasma species that can reactwith the substrate surface to form a passivation layer and/or provide adeposition layer. By way of example, nitrogen (N₂) and/or nitrogencontaining gases such as NH₃, NO, N₂O₃, N₂O, nitrogen basedhydrocarbons, mixtures thereof, or the like can be used to form siliconoxy-nitride or silicon nitride or the like. Similarly, CO₂, CH₄, HCN,C₂O, CO, or mixtures thereof can be used to form silicon carbide (SiC)or silicon carbon nitride (SiCN) or the like. The term “inert” generallyrefers to plasma species that are substantially non-reactive to thesubstrate surface. Examples include, without limitation, inert gasessuch as helium, argon, krypton, xenon, neon, and the like.

The gas supply 18 is in operative communication with the control system26 such that the first selected gas provided during the first selectedtime interval is a reactive gas and the second selected gas providedduring the second selected time interval is a reactive gas. In this andany other embodiment, the first and second time intervals are cycleduntil the desired amount of organic material is removed from thesubstrate surface. In one embodiment, the system is programmed such thatthe last traces of organic material and the protective layer aresimultaneously removed in the final cycle of the plasma mediatedstripping process such that the original substrate surface compositionis restored. Additional intervals (e.g., third, fourth, etc.) withdifferent gases and/or flow rates can be included, if desired.

In another embodiment, the control system is operative such that thefirst selected gas provided during the first time interval is an inertgas and the second selected gas provided during the second selected timeinterval is a reactive gas. It should be noted that in some embodiments,the gas supply provides a plurality of gases that are used to define thefirst selected gas and/or the second selected gas. A gas delivery systemmay include a mass flow controller (not shown) for metering andcontrolling the amount as well as composition of gas into the plasmasource. The mass flow controllers are capable of switching the valves 20between an open state and a closed state in less than one second.Alternatively, a pressure controlled design can be employed.

In one embodiment, the plasma processing system is configured such thatthe process chamber and the gas delivery system provide a gas flow tothe plasma source such that gas flow≧chamber volume+2 seconds. In oneembodiment, the process chamber has a volume of less than 20 liters. Theprocess chamber and the gas delivery system are operative to provide agas flow rate of at least 1 standard liter per minute (slm).

FIG. 2 schematically illustrates one embodiment of a process thatincludes plasma mediated formation of a thin layer of a siliconoxy-nitride (SixO_(y)N_(z)) (wherein 1≦x≦2, and 0≦y≦2, and 0≦z≦3) in thesubstrate surface before and/or during the plasma strip process. Asshown, a substrate 30 having a photoresist mask 32 disposed thereon isexposed to a plasma treatment comprising a nitrogen gas and/or nitrogengas and an inert gas to form a passivation layer 34. The photoresist isthen removed by a plasma mediated photoresist stripping process. Boththe passivation and stripping processes can be performed in the sameplasma reactor. It has been found that passivating the substrate beforeand/or during the plasma strip process reduces formation of an oxidelayer formed during stripping, thereby leading to significantly lesssubstrate material loss relative to processing by the oxygen basedplasma alone.

The plasma generated from the nitrogen gas is substantially non-reactiveto photoresist. Other suitable nitrogen-containing plasmas may includeammonia (NH₃), a so-called forming gas, which comprises a mixture of thehydrogen gas with the nitrogen gas, and nitrogen-containinghydrocarbons. For a non-load locked plasma chamber configuration, thehydrogen gas ranges in an amount from about 3 percent to about 5 percentby volume of the hydrogen for safety considerations. Upon exposure ofthe substrate to the nitrogen species generated in the plasma, a nitridepassivation layer forms. For a silicon substrate, the nitride layer maytake the form of a silicon nitride (e.g., SiNx) and/or may form asilicon-oxy-nitride (SixO_(y)N_(z)) (wherein 1≦x≦2, and 0≦y≦2, and0≦z≦3) depending on whether a native oxide or otherwise is present onthe silicon substrate.

In one embodiment, the process for forming the protective layer iscycled with the plasma mediated stripping process for removing organicmaterial such as photoresist. By way of example, a silicon substrate canbe exposed in a suitable plasma reactor to plasma consisting essentiallyof nitrogen species to form a passivation layer in exposed surfaces ofthe silicon substrate. The thickness of the passivation layer formed isgenerally less than 10 angstroms. Once formed, a standard oxygen basedplasma stripping process can be employed to remove a portion any organicmask material disposed on the substrate, e.g., photoresist. Theprotective layer formation/plasma stripping process is cycled until theorganic material is removed in the desired amount for the particularapplication. By stripping the organic material in this manner, theprotective layer can be reformed between intervals of the plasmamediated stripping cycle since the previously formed passivation layerhas a limited thickness and is simultaneously removed during the plasmamediated stripping process. By cycling the protective layer formationprocess with the plasma stripping process, the oxide formation can besubstantially prevented. For example, in the silicon substrate notedabove, the cycled process can be used to substantially prevent formationof silicon dioxide in the exposed portions of the silicon substrate(e.g., without photoresist mask), which is a byproduct of the oxygenbased plasma strip process.

In another embodiment, the system 10, as shown in FIG. 1 furtherincludes a UV light source for exposing the workpiece to UV radiationfor at least a portion of the first selected time interval for formingthe protective layer on the substrate. In one embodiment, the UV lightsource is provided by the plasma itself. That is, gases are introducedinto the plasma source and energized to provide UV radiation.

Alternatively, a UV lamp may be attached to the plasma process chamberand the UV treatment may be performed immediately before, sequentiallyduring, or continuously during the plasma photo resist removal process.By way of example, the UV lamp from a UV radiator tool can be utilized.During use, the light source chamber may be first purged with an inertgas such as nitrogen, helium, or argon to allow the UV radiation toenter an adjacent process chamber with minimal spectral absorption. Thesubstrate containing the organic material thereon is positioned withinthe process chamber, which is purged separately with nitrogen containingprocess gases, such as nitrogen, ammonia, and mixtures thereof, with orwithout additional inert gases. In this regard, the UV treatment canoccur at vacuum conditions, or at conditions that are substantiallywithout the presence of oxygen or oxidizing gases. UV generating bulbswith different spectral distributions may be selected depending on theapplication. The UV light source can be microwave driven, arc discharge,dielectric barrier discharge, electron impact generated or the like.During the UV exposure, the temperature of the substrate may becontrolled to about room temperature to about 450° C., optionally by aninfrared light source, an optical light source, a hot surface, or the UVlight source itself. The process pressure can be less than, greaterthan, or about equal to atmospheric pressure. The UV power is about 0.1to about 2,000 mW/cm² with an exposure time less than 300 seconds, forexample.

Referring now to FIG. 3, an exemplary process for using the system withthe UV light source includes exposing a substrate to a UV treatment in anitrogen containing, carbon containing, or an inert atmosphere beforeand/or during the plasma strip process. The process generally includesexposing an inorganic substrate 40 with the photoresist mask 42 thereonto ultraviolet radiation in the presence of a nitrogen containing gasand/or nitrogen gas with or without a non-reactive gas to form apassivation layer. Alternatively, the passivation layer can be formed bya UV-assisted surface modification with a substantially nitrogen freepurge environment. The substrate is then exposed to the plasma mediatedphotoresist stripping process to remove the photoresist. Suitablenitrogen gases include NH₃, N₂, N₂O, N₂O₃, NO, nitrogen basedhydrocarbons, mixtures thereof and the like. Suitable carbon containinggases include, without limitation, CO₂, CH₄, HCN, C₂O CO or mixturesthereof. Suitable inert gases include, without limitation, helium,argon, nitrogen, krypton, xenon, neon, and the like.

The plasma mediated organic material stripping process in any of theabove described embodiments is not intended to be limited. Suitableplasma mediated stripping chemistries include, without limitation,reducing plasma chemistries, neutral plasma chemistries, or an oxidizingplasma chemistries. For example, a typical oxygen plasma for removinghigh dose ion implanted photoresist generally includes forming a plasmaform a gas mixture of 90 percent O₂ and 10 percent forming gas.

Suitable substrates include, but are not limited to, silicon,silicon-germanium, high k dielectric materials, metals, and the like.Advantageously, the process is applicable to any device manufacturewhere loss of silicon, including amorphous silicon, over a doped regionis desirable.

The following examples are presented for illustrative purposes only, andare not intended to limit the scope of the invention.

Example 1

In this example, a silicon substrate was exposed to different plasmastripping chemistries in a RapidStrip320 plasma ashing tool commerciallyavailable from Axcelis Technologies, Inc. and subjected to surfaceanalysis using XPS. The different chemistries were processed included astandard oxygen based plasma stripping chemistry and a nitrogen plasmapassivation chemistry. A control silicon substrate was also analyzedwithout exposure to any stripping process. The nitrogen plasmapassivation chemistry included nitrogen gas at 7000 sccm at atemperature of 240° C. and power setting of 3500 Watts. The standardoxygen plasma stripping chemistry included O₂ at 6300 sccm and forminggas (H₂ 3%, N₂ 97%) at 700 sccm at a temperature of 240° C. and powersetting of 3500 Watts. The XPS results are shown in FIGS. 4 and 5.

In FIG. 4, the atomic concentration of nitrogen was measured for thethree different conditions described above. As shown, there was about3.5 percent atomic nitrogen concentration detected by XPS analysis forthe silicon sample exposed to the nitrogen plasma passivation chemistryfor 5 minutes. In FIG. 5, the Si (2p) signal for the nitrogen plasmachemistry revealed a SiNx signature at about 103.3 eV. The Si (2p)signal for the oxygen based plasma chemistry revealed a relatively largeSiO₂ peak at about 103.7 eV indicating thicker oxide formed.

In FIG. 6, the oxygen and nitrogen depth profile for the siliconsubstrate processed with the nitrogen passivation plasma was analyzedusing SIMS. The results indicate that the formation of silicon nitridewas at the SiO₂/Si interface.

Example 2

In this example, pre-ash and post ash oxide thickness was measured byellipsometry as a function of the number of passivation and ashingcycles in a RapidStrip320 plasma ashing tool commercially available fromAxcelis Technologies, Inc. Substrates were bare silicon wafers. Thestandard oxygen based plasma of Example 1 was applied for a total of 60seconds (pulsed into smaller portions as indicated in the Figure whereappropriate). The N₂ passivation plasma included N₂ at 7000 sccm at atemperature of 240° C. and a power setting of 3500 Watts. The totalpassivation cycle time and ash time were kept constant at 60 seconds(the exception being the ash only process where there was no passivationcycle). That is, a cycle time of 6 seconds means that 10 cycles of 6seconds were made for a cumulative time of 60 seconds. Likewise, a cycletime of 15 seconds means that 4 cycles of 15 seconds were made for acumulative time of 60 seconds. After processing, the oxide thickness wasmeasured using an ellipsometer. The results are shown in FIG. 7.

The results clearly show a decrease in oxide growth for both the 15second and 6 second passivation/ashing cycles. There was no observeddifference in oxide thickness after ash for the 60 and 30 second cycles,which was comparable to the ash only result. While not wanting to bebound by theory, it is believed that the passivation layer was too thinto withstand the ash process. By cycling the passivation in relativelyshorter cycles, e.g., 15 and 6 second cycles, for the same amount ofcumulative time, it is believed that the oxide thickness is increasedrelative to longer cycles, e.g., 60 second and 30 second cycles. Asshown, the post ash oxide thickness was reduced by about 3 angstroms forthe 6 second cycle compared to the ashing process without passivation.By forming the passivation layer in situ prior to plasma stripping,silicon loss is minimized and depending on the thickness of thepassivation layer can approach zero silicon loss, which meets andexceeds tolerances for advanced device manufacture.

Example 3

In this example, oxide growth (difference between post and pre-ash oxidethickness) on silicon substrates was measured as a function of exposureto different oxidizing and reducing plasma chemistries with and withouta UV pretreatment. For the UV pretreatment, five different gas ambientwere examined and included helium plus 50 ppm NH₃, helium plus 100 ppmNH₃, helium plus 750 ppm NH₃, helium only, and nitrogen only. The UVpretreatment included exposure in the particular gas ambient in aprototype of an Axcelis RapidCure320FC system at 400° C. for 5 minutes.Two different UV bulbs were tested, which are commercially availablefrom Axcelis under the names of RC02 and RC08. Wavelength range isbetween 100 and 400 nm. The substrates were then exposed to thedifferent oxidizing and reducing plasma chemistries in a RapidStrip320plasma ashing tool commercially available from Axcelis Technologies,Inc. The standard oxygen plasma stripping chemistry included O₂ at 6300sccm and forming gas (H₂ 3%, N₂ 97%) at 700 sccm at a temperature of240° C. and power setting of 3500 Watts. The forming gas plasmapassivation chemistry included forming gas (a mixture of 97% N₂ and 3%H₂) at 7000 sccm at a temperature of 240° C. and power setting of 3500Watts. All plasma exposures were 30 seconds in duration. The results areshown in FIG. 8.

Relative to the silicon substrates that did not include the UVpretreatment, oxide growth was 2 to 3 angstroms less for the UVpretreated substrates exposed to the reducing plasma. UV pretreatment inhelium plus 100 ppm NH₃ provided was most effective for inhibiting oxidegrowth induced by both oxidizing and reducing plasmas.

FIG. 9 graphically illustrates surface analysis using XPS for thesilicon substrate UV pretreatment in helium plus 100 ppm NH₃ compared tothe substrate without the UV pretreatment. Atomic nitrogen surfaceconcentration was found to be about 3.5% (dose 6E14) for the UVpretreated substrate. This result suggest formation of nitride in thesurface oxide (silicon-oxy-nitride (Si_(x)O_(y)N_(z)) (1≦x≦2, and 0≦y≦2.and 0≦z≦3)), which reduces oxide growth during the subsequentphotoresist stripping process.

FIG. 10 shows high resolution XPS spectrum the binding energies for theN (1 s) signal for the samples with and without the exposure to thepretreatment process (helium plus 100 ppm NH₃). The data providesevidence that surface nitride forms on the silicon surface afterexposure to the pretreatment process.

It will be understood that when an element is referred to as being “on”another element, it can be directly on the other element or interveningelements can be present therebetween. In contrast, when an element isreferred to as being “disposed on” or “formed on” another element, theelements are understood to be in at least partial contact with eachother, unless otherwise specified.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The use of the terms “first”, “second”, and the like do notimply any particular order but are included to identify individualelements. It will be further understood that the terms “comprises”and/or “comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which the embodiments of the inventionbelong. It will be further understood that terms, such as those definedin commonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand the present disclosure, and will not be interpreted in an idealizedor overly formal sense unless expressly so defined herein.

While embodiments of the invention have been described with reference toexemplary embodiments, it will be understood by those skilled in the artthat various changes can be made and equivalents can be substituted forelements thereof without departing from the scope of the embodiments ofthe invention. In addition, many modifications can be made to adapt aparticular situation or material to the teachings of embodiments of theinvention without departing from the essential scope thereof. Therefore,it is intended that the embodiments of the invention not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out this invention, but that the embodiments of the inventionwill include all embodiments falling within the scope of the appendedclaims. Moreover, the use of the terms first, second, etc. do not denoteany order or importance, but rather the terms first, second, etc. areused to distinguish one element from another. Furthermore, the use ofthe terms a, an, etc. do not denote a limitation of quantity, but ratherdenote the presence of at least one of the referenced item.

1. A process for reducing the loss of substrate material in a plasmamediated photoresist stripping process, the process comprising:providing a substrate having at least a portion of a surface coveredwith a material; forming a protective layer on the surfaces free of thematerial before and/or during the photoresist stripping process, whereinforming the protective layer comprises exposing the substrate to plasmaformed from a nitrogen containing gas and/or a carbon containing gas orexposing the substrate to ultraviolet radiation in the presence of thenitrogen containing gas and/or the carbon containing gas; simultaneouslyremoving at least a portion of the material with the plasma mediatedstripping process and the protective layer; and repeating the steps offorming the protective layer and removing the at least portion of thematerial disposed thereon until a desired thickness of the material isremoved.
 2. The process of claim 1, wherein the material is aphotoresist and/or an anti-reflective coating.
 3. The process of claim1, wherein forming the protective layer comprises depositing theprotective layer onto the surfaces free of the material.
 4. The processof claim 1, wherein forming the protective layer comprises passivatingthe surfaces free of the material.
 5. The process of claim 1, whereinthe nitrogen containing gas comprises N₂, NH₃, NO, N₂O₃, N₂O, nitrogencontaining hydrocarbons, or mixtures thereof.
 6. The process of claim 1,wherein the carbon containing gas comprises CO₂, CH₄, HCN, C₂O, CO ormixtures thereof.
 7. The process of claim 1, wherein the plasma mediatedprocess comprises exposing the substrate to an oxygen based plasma. 8.The process of claim 1, wherein the plasma mediated stripping processcomprises exposing the substrate to an oxygen based plasma.
 9. Theprocess of claim 1, wherein each one of the steps for forming theprotective layer and removing the at least portion of the material isless than one second.
 10. A process for reducing the loss of substratematerial in a plasma mediated stripping process, the process comprising:providing a substrate including a mask of an organic material disposedthereon; forming a protective layer on an exposed surface of thesubstrate without the mask before and/or during the photoresiststripping process, wherein forming the protective layer comprisesexposing the surface to ultraviolet radiation in the presence of aninert gas or a nitrogen containing gas or a carbon containing gas ormixtures thereof, removing at least a portion of the mask and theprotective layer with the plasma mediated stripping process; andrepeating the steps of forming the protective layer and removing the atleast portion of the mask until a desired thickness of the mask isremoved.
 11. The process of claim 10, wherein the organic material is aphotoresist and/or an anti-reflective coating.
 12. The process of claim10, wherein forming the protective layer comprises depositing theprotective layer onto the surfaces free of the organic material.
 13. Theprocess of claim 10, wherein forming the protective layer comprisespassivating the surfaces free of the organic material.
 14. The processof claim 10, wherein the nitrogen containing gas comprises N₂, NH₃, NO,N₂O₃, N₂O, nitrogen containing hydrocarbons, or mixtures thereof. 15.The process of claim 10, wherein the inert gas is selected from a groupconsisting of helium, argon, nitrogen, krypton xenon, and neon
 16. Theprocess of claim 10, wherein the carbon containing gas comprises CO₂,CH₄, HCN, C₂O, CO or mixtures thereof.
 17. The process of claim 10,wherein the plasma mediated stripping process comprises exposing thesubstrate to an oxidizing plasma or a reducing plasma.
 18. A plasmaprocessing system for processing an inorganic workpiece substrate havingorganic material residing thereon by removing the organic material whileleaving the inorganic substrate substantially unaltered, comprising: aprocess chamber for processing the workpiece placed therein; a plasmasource for delivering excited state gas into said process chamber toproduce a reactive environment therein; a gas delivery system, includinga plurality of gas valves, for selectively delivering at least one gasfrom a gas supply to said plasma source; a power generator assembly forpowering the plasma source to excite the gas delivered by said gasdelivery system; and a control system for selectively activating saidgas valves of said gas delivery system so as to provide at least a firstselected gas for at least a first selected time interval for forming aprotective layer on the substrate, and at least a second selected gasfor at least a second selected time interval for removing the organicmaterial residing on the workpiece substrate.
 19. The plasma processingsystem of claim 18, further comprising a UV light source for exposingthe workpiece substrate to UV radiation for at least a portion of thefirst selected time interval for forming the protective layer on thesubstrate.
 20. The plasma processing system of claim 19, wherein the gassupply includes a plurality of gases, including reactive gases and/orinert gases, and further wherein: the control system is operative suchthat the first selected gas provided during the first selected timeinterval is a reactive gas; and the control system is further operativesuch that the second selected gas provided during the second selectedtime interval is a reactive gas.
 21. The plasma processing system ofclaim 19, wherein the gas supply includes a plurality of gases,including reactive gases and/or inert gases, and further wherein: thecontrol system is operative such that the first selected gas providedduring the first selected time interval is an inert gas; and the controlsystem is further operative such that the second selected gas providedduring the second selected time interval is a reactive gas.
 22. Theplasma processing system of claim 18, wherein the protective layerincludes a passivation layer formed in a surface layer of the workpiecesubstrate.
 23. The plasma processing system of claim 18, wherein theprotective layer is a deposition layer formed on a surface layer of theworkpiece substrate.
 24. The plasma processing system of claim 18,wherein said valves of said gas delivery system include a mass flowcontroller for measuring and controlling a flow of a selected gasdelivered through the gas delivery system.
 25. The plasma processingsystem of claim 24, wherein said mass flow controllers are capable ofswitching between an open state and a closed state in less than onesecond.
 26. The plasma processing system of claim 18, wherein saidprocess chamber has a volume of less than 20 liters.
 27. The plasmaprocessing system of claim 18, wherein said process chamber and gasdelivery system are operative to provide a gas flow rate of at least 1slm.
 28. The plasma processing system of claim 18, wherein said chamberhas a volume and the gas delivery system is configured to provide a gasflow such that gas flow≧chamber volume÷2 seconds.